Powering a computer up and powering it down are basic operations of the computer. To that end, a computer typically has a power button on its house (e.g., on its front panel) that a user can press to initiate a power-up or power-down operation of the computer. Depending on the power-saving scheme implemented in the computer, the power button may be used to bring the computer from the normal operational (i.e., “on”) state to one of the power-saving states, such as the S1–S3 states of the Advanced Configuration and Power Interface (ACPI) specification, or to a power-down state, such as the S4 or S5 state of the ACPI.
In some computer configurations, for ease of access or other reasons, it is often desirable to have a system power button at a location separate from the computer housing, such as on a keyboard or the like. For example, the computer may be placed at a location that makes the power button on the computer housing hard to reach, and it would be more convenient for the user to use a power button on the keyboard to turn the computer on or off. The wiring between the computer and the keyboard, however, may limit the functionality of such a button. For instance, today's USB keyboards (i.e., keyboards connected to computers via Universal Serial Bus (“USB”) cables) often have a Sleep button that can be used to place the computer into the S1–S5 ACPI states. The Sleep button, however, can only be used to wake the system from the S1, S2 and S3 states, and cannot be used to power up the computer from the S4 or S5 state. This is because the signal generated by pressing the Sleep button has to be transmitted from the keyboard to the computer over the USB bus, which is not operational when the computer is powered down. Thus, there is a need for a way to provide a power button on a USB keyboard that can be used to initiate system power-up.